Interaction between FREM1 and PDGFC. (A) Structural representations of the full-length FREM1, FLAG-tagged construct and truncated constructs: NV alone, NV-CSPG, CSPG and CalXβ-C-lectin domains are shown with the tags indicated. The MYC tag shown refers to a 3×MYC tag + Igκ secretion signal. (ab), location of immunising sequence for anti-FREM1 antibodies upstream of mutation. (B) E13.5 WT and bat embryo head skin sections stained for FREM1 (green), PDGFC (red) and nuclear dye DAPI (blue). (C) NIH3T3 fibroblasts expressing FREM1-FLAG and PDGFC-V5 and immunostained as indicated. (D) Coimmunoprecipitation of FREM1-FLAG and PDGFC-V5 in transfected HEK293 cells. (E,F) Co-immunoprecipitation of PDGFC-V5 with MYC-tagged FREM1 subdomains. (G) Co-immunoprecipitation of endogenous FREM1 and PDGFC from embryo extracts at E12.5. A rabbit pre-immune serum was included as a control. * IgG heavy chain; IP, immunoprecipitation antibody; WB, western blotting antibody.